package com.kaili.common.util;

public class SnowflakeIdFactory {
    private final long twepoch = 1525515498888L;
    private final long workerIdBits = 5L;
    private final long datacenterIdBits = 5L;
    private final long maxWorkerId = -1L ^ (-1L << workerIdBits);
    private final long maxDatacenterId = -1L ^ (-1L << datacenterIdBits);
    private final long sequenceBits = 12L;
    private final long workerIdShift = sequenceBits;
    private final long datacenterIdShift = sequenceBits + workerIdBits;
    private final long timestampLeftShift = sequenceBits + workerIdBits + datacenterIdBits;
    private final long sequenceMask = -1L ^ (-1L << sequenceBits);
    private long workerId;
    private long datacenterId;
    private long sequence = 0L;
    private long lastTimestamp = -1L;
    private static SnowflakeIdFactory instance = null;
    private static Object lock = new Object();
    public static String getNextId(){
        if(instance == null){
            synchronized (lock){
                if(instance==null){
                    instance = new SnowflakeIdFactory(5,5);
                }
            }
        }
        return String.valueOf(instance.nextId());
    }
    public SnowflakeIdFactory(long workerId, long datacenterId) {
        if (workerId > maxWorkerId || workerId < 0) {
            throw new IllegalArgumentException(String.format("worker Id can't be greater than %d or less than 0", maxWorkerId));
        }
        if (datacenterId > maxDatacenterId || datacenterId < 0) {
            throw new IllegalArgumentException(String.format("datacenter Id can't be greater than %d or less than 0", maxDatacenterId));
        }
        this.workerId = workerId;
        this.datacenterId = datacenterId;
    }

    public synchronized long nextId() {
        long timestamp = timeGen();
        if (timestamp < lastTimestamp) {
            //服务器时钟被调整了,ID生成器停止服务.
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;
        return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
    }
    /*public synchronized String nextString() {
        long timestamp = timeGen();
        if (timestamp < lastTimestamp) {
            //服务器时钟被调整了,ID生成器停止服务.
            throw new RuntimeException(String.format("Clock moved backwards.  Refusing to generate id for %d milliseconds", lastTimestamp - timestamp));
        }
        if (lastTimestamp == timestamp) {
            sequence = (sequence + 1) & sequenceMask;
            if (sequence == 0) {
                timestamp = tilNextMillis(lastTimestamp);
            }
        } else {
            sequence = 0L;
        }

        lastTimestamp = timestamp;
        Date date = new Date()
        //return ((timestamp - twepoch) << timestampLeftShift) | (datacenterId << datacenterIdShift) | (workerId << workerIdShift) | sequence;
    }*/

    protected long tilNextMillis(long lastTimestamp) {
        long timestamp = timeGen();
        while (timestamp <= lastTimestamp) {
            timestamp = timeGen();
        }
        return timestamp;
    }

    protected long timeGen() {
        return System.currentTimeMillis();
    }

    public static void main(String[] args) {

        //System.out.format("%d\r\n",SnowflakeIdFactory.getNextId());

//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
//        System.out.println(Long.toHexString(SnowflakeIdFactory.getNextId()));
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
        System.out.println(SnowflakeIdFactory.getNextId());
    }
}
